Japanese Patent Application Publication No. 2000-295715 (JP 2000-295715 A) (Patent Document 1) describes an electric car power source system for supplying power to a load (vehicle driving motor) from two direct current power sources. In Patent Document 1, two electric double layer capacitors are utilized as direct current power sources. Patent Document 1 describes an operation mode for supplying power to the load by connecting two electric double layer capacitors in parallel.
Japanese Patent Application Publication No. 2008-54477 (JP 2008-54477 A) (Patent Document 2) describes a voltage conversion device configured to receive a plurality of direct current voltages for outputting a plurality of direct current voltages. In the power conversion device of Patent Document 2, it is possible to change an operation mode by changing over connection between terminals of an energy accumulation means (coil) and a plurality of input electric potentials and a plurality of output electric potentials. The operation mode includes a mode for supplying power to a load from two direct current power sources which are connected in parallel.